As is well known in the medical profession, both the hematocrit and oxygen saturation levels of blood can be measured optically. Oftentimes, such information is of vital importance for the proper medical treatment of an individual. Examples of devices for performing such measurements are shown in U.S. Pat. No. 4,447,150 to Heinemann, which discloses an apparatus and method for measuring blood oxygen saturation and U.S. Pat. No. 4,745,279 to Karkar et al., which discloses a hematocrit measuring apparatus.
In these devices and others used to perform such operations, the oxygen saturation level and the hematocrit level are obtained by measuring the amount of scattering of light of various wavelengths which occurs within a quantity of blood. Thus, as can be appreciated, it is particularly important that the light source used to infuse the various wavelengths of light into the blood be such that it provide a uniform distribution of such light so as to facilitate accurate scattering effects within the blood. Also, with regard to both oxygen saturation and hematocrit measurements, the accuracy of these measurements is further affected by the presence of proteins and the pH level of the blood. Moreover, in measuring hematocrit there is an effect on the measurement attributable to the oxygen saturation level, while in measuring oxygen saturation, there is an effect on the measurement attributable to the hematocrit level; i.e. oxygen saturation level and hematocrit level of a blood sample are interelated.
As is well known, the use of optical fibers generally provides a light source having the advantage that light is emitted from such fibers at a more uniform distribution than that emitted from conventionally-known light emitting diodes (LED's). In the hematocrit measuring device disclosed in Karkar et al., LED's are used as a means of infusing light into the blood. Thus, though this device provides a generally reliable measuring means, the hematocrit measurement obtained by this device is more prone to inaccuracy due to the utilization of LED's as a light source. Also, though this prior art device provides a hematocrit measurement which is compensated for the effects of oxygen saturation, it does not provide a separate oxygen saturation measurement compensated for the effects of hematocrit, nor does it possess the capacity to compensate the hematocrit measurement for the effects of proteins and pH. Though the Heinemann 4,447,150 patent contemplates the use of fiber optics in coupling light to a quantity of blood, the device disclosed by this reference provides only an oxygen saturation measurement which is compensated for the effects of hematocrit, but not for the effects of proteins and pH. Additionally, the device taught by this particular reference is adapted to obtain an oxygen saturation measurement only from blood in a flowing mode and not from a quantity of blood in a static mode, i.e. environment. A device utilizing fiber optics for obtaining hematocrit and oxygen saturation measurements of blood is also disclosed in U.S. Pat. No. 4,776,340 to Moran et al. Though this device provides both an independent hematocrit measurement and an oxygen saturation measurement that is compensated for hematocrit, it does not provide a hematocrit measurement which is compensated for oxygen saturation, nor does it compensate either measurement for the effects of proteins and pH. More importantly, this particular reference discloses a catheter used in the critical care environment of a hospital. In this regard, utilization of this device involves the direct insertion of an optical fiber into the bloodstream of a patient, i.e. in situ application, thus limiting use of the device to blood in a flowing mode environment. Additionally, because the optical fiber comes into direct contact with the blood of the patient, the fiber must be replaced after each application and the measuring device re-calibrated for each use of a new catheter/optical fiber.
With respect to the Heinemann and Moran references, the importance of being able to obtain hematocrit and oxygen saturation measurements from blood in a static rather than a flowing mode, wherein blood is drawn into a syringe or cuvette and tested while therein, achieves added significance when one considers the risks associated with handling blood, particularly due to the current AIDs epidemic. Though Karkar et al. contemplates testing blood in a static mode, no consideration is given for the settling of red blood cells in the blood containment vessel which could also adversely effect hematocrit and oxygen saturation measurements.
Other hematocrit and oxygen saturation measuring devices known in the art also include many of the aforementioned shortcomings. Additionally, many of these devices are extremely costly and difficult to utilize. Thus, there exists a need in the art for a cost efficient measuring device providing a hematocrit measurement of increased accuracy which is compensated for the effects of oxygen saturation, pH, and proteins, and additionally provides an oxygen saturation measurement of increased accuracy which is compensated for the effects of hematocrit, pH, and proteins. Moreover, there exists a need for an analytical measuring device which can obtain such measurements from a quantity of blood wherein the blood may be tested in a static mode while being maintained within the interior of a containment apparatus such that a minimal amount of direct contact with the blood need be undertaken, and further wherein red blood cells within the quantity of blood being tested in a static mode are prevented from settling in the containment apparatus.